Pkocess for washing abducts of urea



BJTFEZB Patented Jan. 14, tees 3,117,923 PROCESS FOR WASHING ADDUCTS F UREA. AND STRAlGHT-CHAlN PARAFFINES EN THE DEPARAFFENLQG 0F HYDROCAREQN (311$ Hermann Fran: and Max Kunert, Frankfurt am Main, Germany, assiguors to Edeleanu Gesellschalt m.b.H., Frankfurt am Main, Germany, a corporation of Germany No Drawing. Filed Jan. 19, 1961, Ser. No. 83,628 Claims priority, application Germany Jan. 30, 1960 1 Claim. (Cl. 208-25) As is wel known, upon contact of urea with straightchain and only weakly branched parafiines, an adduct is formed which is a solid and by the separation thereof the solidification point of a hydrocarbon oil, i.e. its paratfine content, can be reduced substantially. Vfhen this adduct has been separated out of the adduct-forming mixture, there always adhere to it very considerable quantities of the oil fractions that remain liquid and are not combined with urea. On the one hand they worsen the quality of the paraifines that are obtained after the decomposition of the adduct; on the other hand they lower the yield of deparaifined oil.

Therefore it has been attempted from the beginning to wash out the oil fractions remaining in the adduct. For this purpose, for example, urea solutions have been caused to travel over the solid, caked adduct present on the separating mechanism. in view of the fact that the urea solvents used as the so-called activators, such as water, methanol and the like, as a rule have no or only limited power to dissolve hydrocarbon oil fractions, it was not to be expected that the washing effect thereby achieved would result in any substantial improvement in the quality of the oil and the yield of filtrate. Intensive stirring of the called adduct loosened from the separating device, with a urea solution in special churning vessels was also unsatisfactory.

Better washing was achieved when the caked adduct was treated with solvents which have high dissolving power for the oil fractions, the so-called :oil solvents.

Used as oil solvents were, as usual:

H ai o g e n hydrocarbons, aromatics, naphthenes, branched hydrocarbons and also straight-chain hydrocarbons Which do not combine with urea under the conditions of the adduct formation.

if the washing is undertaken in the last-mentioned manner, it proves disadvantageous that the adduct retains relatively large amounts of the oil solvent. After the decomposition of the adduct (into an n-parafiine layer and a layer of aqueous urea solution), these quantities of oil solvent are found again chiefly in the n-paraffine layer. They must be recovered from this layer, the quantities of the oil solvent being always quite large, between 30 and 50% by weight relative to the adduct. In the case of filtration under the mfluence of gravity, they are at the upper limiting value, i.e. at about 50% by weight; in the case of filtration under the influence of vacuum or pressure or by means of a centrifuge, they are at the lower limit, i.e. at about 30% by weight. The cost of recovering these quantities is therefore rather large.

It is the object of the invention to obtain an adduct, with the help of simple procedures, which contains on the one hand only a small amount of oil fractions and on the other hand only a small amount of oil solvent.

In accordance with the invention it is proposed first to undertake the washing of the adduct, which during the treatment consists of hydrocarbon oils with a urea solution, with an oil solvent and then to displace the remaining oil solvent from the adduct by means of an aqueous urea solution.

The concentration of the urea solution is without practical importance in such case. It is suitable to use a urea solution which is saturated at the temperature at which the washing is undertaken.

This washing temperature in general lies at room temperature. Since the adduct-forming temperature can also rise with a rise in the carbon number of the n-paraffines, it is conceivable that there are also cases in which the washing of the adduct can be undertaken at a temperature higher than 20 C. However, due to the presence of the aqueous urea solution, 80 C. cannot be exceeded, because urea begins to decompose noticeably at 80 C. in the presence of Water.

The quantity of urea solution used to displace the oil solvent is in general small. It suifices to use only enough urea solution to exactly displace the oil solvent. case the filtrate consists only of oil solvent, while the urea solution remains completely in the adduct. However, it is also possible to use greater quantities of urea solution. The filtrate, which in this case consists of urea solution and oil solvent, is easy to separate because of the separated layers present. The oil solvent can be re-used in the cycle.

Through the inventive procedures the oil solvent content is substantially reduced, i.e. to about 5% by weight relative to the adduct, and this is independent of the preceding filtration.

A further reduction is not possible since this remaining amount of oil solvent is very strongly adsorptively combined. For this reason a repetition of the washing with urea solution is purposeless.

Besides these small quantities of oil solvent there is still some urea solution in the adduct. its quantity is at most by wei ht relative to the adduct. This urea solution is no troublesome factor; it is even desirable in the decomposition of the adduct which follows the filtration because it accomplishes the decomposition together with the urea solution specially added for that purpose.

The invention is illustrated by the following examples:

Example 1 300 grams of an adduct, which was obtained in the urea treatment of a spindle oil (d.=0.8672; viscosity at (1:20.64 cst.) in the presence of methylene chloride as an oil solvent and which had a diameter of the adduct grains of 0.2 mm., was screened on a sieve having a mesh dimension or" 0.15 (about the equivalent of a 100 mesh Tyler sieve) under the influence of gravitation at 40 C. The sieved product was in a layer about cm. high. This adduct still contained 45% by weight of the oil solvent (methylene chloride), relative to the adduct, after the adduct was dripped off. This mass of oil solvent is composed firstly of solvent to be used for washing the adduct and only secondarily of solvent still adhering to the adduct after formation of the adduct. Them 100 grams of a urea solution, saturated at C, was added over the adduct at 20 C. The methylene chloride was replaced in the adduct until 7% by weight remained. The urea solution was so apportioned that it remained completely in the adduct and the filtrate consisted only of methylene chloride.

Example 2 300 grains of the same adduct as in Example 1 was filtered in a suction filter under a vacuum of 15-20 mm. of mercury at C. The sieved product was in a layer 15 cm. high and had a methylene chloride content of 32% by weight. This mass or" oil solvent is composed firstly of solvent to be used for washing the adduct and only secondarily of solvent still adhering to the adduct after formation of the adduct. It was washed at 20 C. with grams of a urea solution saturated at 35 C. The con- In this tent of methylene chloride diminished to 5% by weight. The filtrate consisted of methylene chloride.

Example 3 300 grams of the adduct mentioned in Example 1 was filtered at 40 C. in a filtering centrifuge (speed: 10,000 r.p.rn.). The methylene chloride content was 31% by weight. This mass of oil solvent is composed firstly of solvent to be used for washing the adduct and only seeondarily of solvent still adhering to the adduct after formation of the adduct. At 20 C. this amount of methylene chloride was largely replaced by 80 grams of a urea solution saturated at 35 C. The methylene chloride content diminished to 5% by weight in the sieved product; the filtrate consisted only of methylene chloride.

Example 4 200 grams of an adduct (grain diameter 0.1 mm.), which was obtained by treating with urea a petrolatum (solidification point 71 0., oil content 3.65% by Weight), completely dissolved in ethylene chloride-1,2, was filtered through a sieve with a mesh width of 0.075 mm. (about equivalent to a 200 mesh Tyler sieve) at 60 C. The sieved product was in a layer 35 cm. deep and had a content of ethylene chloride-1,2 of 48% by weight. This mass of oil solvent is composed firstly of solvent to be used for Washing the adduct and only secondarily of solvent still adhering to the adduct after formation of the adduct. t was washed at 50 C. with 70 grams of a urea solution saturated at 60 C. The content of ethylene chloride-1,2 was about 6% by Weight. The filtrate consisted only of ethylene chloride-1,2.

T he invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claim rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claim are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

References Cited in the file of this patent UNITED STATES PATENTS 2,588,602 Adams et a1 Mar. 11, 1952 2,714,586 Lynch Aug. 2, 1955 2,763,637 McKay et a1 Sept. 18, 1956 2,917,447 Hoppe et a1 Dec. 15, 1959 2,999,857 Hoppe Sept. 12, 1961 

